1. Field of the Invention
The present application relates to structural vibration control mechanism, and particularly to magnetorheological (MR) dampers useful in such controls.
2. Background of the Invention
Magnetorheological (MR) dampers have been used in vibration control of civil and mechanical structures. Application examples include vibration damping of the suspension cables in cable-stayed bridges, vibration damping of automotive seats and suspension systems, and vibration isolation of automation and/or precision equipment/machines, to name a few. The MR materials used in the MR dampers have the ability to reversibly change their rheological characteristics upon applying a magnetic field. In more details, they can change themselves from a free-flowing, linear viscous fluid to a semi-solid with adjustable/controllable yield stress in milliseconds when exposed to an applied magnetic field. By inputting different electrical currents to the electromagnet of such an MR damper. It can adjust/control the magnetic field applied to the MR material so that the yield stress of the material and hence the yield force and rheological damping of the damper can readily be adjusted/controlled in milliseconds. While possessing adjustable/controllable yield force and rheological damping capabilities, the existing MR dampers are incapable of sensing structural vibrations for implementing real-time, close-loop vibration controls; they are only limited to an open-loop mode of operation instead, and their adjustable/controllable capability cannot be fully utilized.
Technological advancement of structural vibration controls from an open-loop to a close-loop operation of MR dampers requires the development of an accurate inverse dynamic model for the dampers so as to determine appropriate current inputs for facilitating the desired yield force and rheological damping. Nevertheless, it is still a challenge to develop such an inverse dynamic model for these highly nonlinear dampers. Alternatively, a force feedback control loop is often deployed to overcome the deficiency of implementing inverse dynamic modeling via an installation of force sensors between the vibrating structures and the dampers at the expense of reducing the control effectiveness and increasing both the implementation difficulty and engineering cost.